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排序方式: 共有192条查询结果,搜索用时 15 毫秒
1.
Interaction of the serum amyloid A proteins with phospholipid 总被引:2,自引:0,他引:2
L L Bausserman P N Herbert T Forte R D Klausner K P McAdam J C Osborne M Rosseneu 《The Journal of biological chemistry》1983,258(17):10681-10688
The serum amyloid A proteins (SAA) are transported in plasma in association with the high density lipoproteins. We have studied the solution properties of two of the polymorphic forms of SAA, SAA1 and SAA4, and compared the lipid-binding properties of SAA4 to those of the well characterized apolipoproteins, apo-A-I, apo-A-II, and apo-C-III. SAA4 was monomeric at pH 2.9 but considerable self-association was demonstrated at pH 8.2, even in the presence of 1.0 M guanidine HCl. SAA4 differed from the apolipoproteins in its ability to disrupt multilamellar dimyristoylphosphatidylcholine (DMPC) liposomes and generate bilayer discs. Apo-A-I, apo-A-II, and apo-C-III reduced the turbidity of DMPC dispersions at protein:lipid molar ratios of 1:200. SAA4, however, increased turbidity at molar ratios of 1:250 and 1:100 even when preincubated in guanidine HCl before addition to liposomes. Optical density decreased only at ratios of 1:50 and 1:25. At an SAA4:DMPC ratio of 1:50, discoidal particles (long axis, 28.1 nm; short axis, 4.4 nm) were formed which were similar to those produced by apo-C-III. Lipid binding induced changes in SAA4 conformation similar to those observed in the apolipoproteins. The alpha-helical content and intrinsic tryptophanyl fluorescence were increased and quenching of tryptophanyl fluorescence by acrylamide was reduced in the presence of DMPC. In addition, SAA4 as well as the apolipoproteins broadened the range and increased the temperature of the gel-liquid crystal transition temperature of DMPC. 相似文献
2.
Stockton JC Howson JM Awomoyi AA McAdam KP Blackwell JM Newport MJ 《FEMS immunology and medical microbiology》2004,41(2):157-160
The nucleotide oligomerization binding domain 2 gene (NOD2) encodes an intracellular receptor for bacterial components, which is expressed in monocytes and is associated with Crohn's Disease (CD). This finding, along with epidemiological evidence, supports a role for infection in the pathogenesis of CD. Speculation that mycobacteria are involved in CD led us to investigate NOD2 in susceptibility to tuberculosis (TB), a global public health problem caused by Mycobacterium tuberculosis. CD-associated NOD2 variants were absent in a case-control study of 640 Gambians, where CD is rare. Novel NOD2 promoter polymorphisms were identified but showed no association with TB in this African population sample. 相似文献
3.
4.
Maternal effects can have lasting fitness consequences for offspring, but these effects are often difficult to disentangle from associated responses in offspring traits. We studied persistent maternal effects on offspring survival in North American red squirrels (Tamiasciurus hudsonicus) by manipulating maternal nutrition without altering the post-emergent nutritional environment experienced by offspring. This was accomplished by providing supplemental food to reproductive females over winter and during reproduction, but removing the supplemental food from the system prior to juvenile emergence. We then monitored juvenile dispersal, settlement and survival from birth to 1 year of age. Juveniles from supplemented mothers experienced persistent and magnifying survival advantages over juveniles from control mothers long after supplemental food was removed. These maternal effects on survival persisted, despite no observable effect on traits normally associated with high offspring quality, such as body size, dispersal distance or territory quality. However, supplemented mothers did provide their juveniles an early start by breeding an average of 18 days earlier than control mothers, which may explain the persistent survival advantages their juveniles experienced. 相似文献
5.
The involvement of the bridging imidazolate in the catalytic mechanism of action of bovine superoxide dismutase. 下载免费PDF全文
M E McAdam E M Feilden F Lavelle L Calabrese D Cocco G Rotilio 《The Biochemical journal》1977,167(1):271-274
The pulse-radiolysis method has been used to study the catalytic mechanism of O2 leads to dismutation by the Co(II)-substituted bovine erythrocuprein (superoxide dismutase, EC 1.15.1.1). Catalysis is accompanied by spectral changes that may be interpreted in terms of rapid protonation and deprotonation of the Cu-facing nitrogen atom of the imidazolate that bridges the Cu(II) and the Co(II) [or Zn(II)] in the oxidized enzyme. This rapid change permits the possibility that the imidazole is a proton donor in the catalytic reduction of O2 leads to. 相似文献
6.
L. J. Quittenden E. L. McAdam N. W. Davies J. J. Ross 《Journal of Plant Growth Regulation》2014,33(4):831-836
The biosynthetic route of the key plant hormone, indole-3-acetic acid (IAA) has confounded generations of biologists. Evidence in higher plants has implicated two auxin intermediates with roles established in bacteria: indole-3-acetamide (IAM) and indole-3-pyruvic acid. Herein, the IAM pathway is investigated in pea (Pisum sativum), a model legume. The compound was not detected in pea tissue, although evidence was obtained for its presence in Arabidopsis, tobacco, and maize. Deuterium-labeled tryptophan was not converted to IAM in pea roots, despite being converted to IAA. After feeds of deuterium-labeled IAM, label was recovered in the IAA conjugate IAA-aspartate (IAAsp), although there was little or no labeling of IAA itself. Plants treated with IAM did not exhibit high-IAA phenotypes, and did not accumulate IAA. This evidence, taken together, indicates that although exogenous IAM may be converted to IAA (and further to IAAsp), the IAM pathway does not operate naturally in pea roots. 相似文献
7.
Mothers often provide much of the early environment for their offspring. These maternal effects are predicted to result in unusual evolutionary dynamics in offspring traits if they are themselves heritable, but these important predictions have not previously, to our knowledge, been tested in the wild. Here, we quantified the responses of red squirrels (Tamiasciurus hudsonicus) to documented episodes of natural selection and found support for both of the fundamental predictions of models that describe maternal effect evolution. First, changes in juvenile growth rates across one generation of selection were five times greater than predicted by heritability (h2) alone, but were consistent with the additional contribution of maternal genetic effects. Second, responses to selection were influenced not only by the strength of selection in the current generation, but also by selection in the previous generation, indicating the presence of evolutionary momentum. These results were in agreement with predictions of a simple model including litter size as the only maternal effect, and provide, to our knowledge, the first empirical evidence for the importance of maternal effects to evolutionary dynamics in a natural population. 相似文献
8.
Genetic and plastic responses of a northern mammal to climate change 总被引:11,自引:0,他引:11
Réale D McAdam AG Boutin S Berteaux D 《Proceedings. Biological sciences / The Royal Society》2003,270(1515):591-596
Climate change is predicted to be most severe in northern regions and there has been much interest in to what extent organisms can cope with these changes through phenotypic plasticity or microevolutionary processes. A red squirrel population in the southwest Yukon, Canada, faced with increasing spring temperatures and food supply has advanced the timing of breeding by 18 days over the last 10 years (6 days per generation). Longitudinal analysis of females breeding in multiple years suggests that much of this change in parturition date can be explained by a plastic response to increased food abundance (3.7 days per generation). Significant changes in breeding values (0.8 days per generation), were in concordance with predictions from the breeder's equation (0.6 days per generation), and indicated that an evolutionary response to strong selection favouring earlier breeders also contributed to the observed advancement of this heritable trait. The timing of breeding in this population of squirrels, therefore, has advanced as a result of both phenotypic changes within generations, and genetic changes among generations in response to a rapidly changing environment. 相似文献
9.
Campbell SJ Sabeti P Fielding K Sillah J Bah B Gustafson P Manneh K Lisse I Sirugo G Bellamy R Bennett S Aaby P McAdam KP Bah-Sow O Lienhardt C Hill AV 《Immunogenetics》2003,55(7):502-507
Evidence for linkage between tuberculosis and human chromosomal region Xq26 has previously been described. The costimulatory molecule CD40 ligand, encoded by TNFSF5 and located at Xq26.3, is a promising positional candidate. Interactions between CD40 ligand and CD40 are involved in the development of humoral- and cell-mediated immunity, as well as the activation of macrophages, which are the primary host and effector cells for Mycobacterium tuberculosis. We hypothesised that common variation within TNFSF5 might affect susceptibility to tuberculosis disease and, thus, might be responsible for the observed linkage to Xq26. Sequencing 32 chromosomes from a Gambian population identified nine common polymorphisms within the coding, 3 and 5 regulatory sequences of the gene. Six single nucleotide polymorphisms (SNPs) and a 3 microsatellite were genotyped in 121 tuberculosis patients and their available parents. No association with tuberculosis was detected for these variants using a transmission disequilibrium test, although one SNP at –726 showed some evidence of association in males. This finding, however, did not replicate in a separate case control study of over 1,200 West African individuals. We conclude that common genetic variation in TNFSF5 is not likely to affect tuberculosis susceptibility in West Africa and the linkage observed in this region is not due to variation in TNFSF5.Sadly, Professor Steve Bennett passed away in March 2003 相似文献
10.
Nader Rahimi Eric Tremblay Laura McAdam Anita Roberts Bruce Elliott 《In vitro cellular & developmental biology. Animal》1998,34(5):412-420
Summary We have developed an in vitro system to examine the influence of adipocytes, a major mammary stromal cell type, on the growth of a murine mammary carcinoma,
SP1. Previously, we have shown that 3T3-L1 adipocytes release a mitogenic factor, hepatocyte growth factor, which strongly
stimulates proliferation of SP1 cells. We now show that 3T3-L1 pre-adipocytes secrete active inhibitory molecules which inhibit
DNA synthesis in SP1 cells. In addition, latent inhibitory activity is present in conditioned media (CM) from both pre-adipocytes
and adipocytes, and is activated following acid treatment. CM also inhibited DNA synthesis in Mv1Lu wild type epithelial cells,
but not DR27 mutant epithelial cells which lack TGF-β type II receptor. Inhibitory activity of CMs was partially abrogated
by neutralizing anti-TGF-β1 and anti-TGF-β2 antibodies, and was removed following ultrafiltration through membranes of 10
000 Mr but not 30 000 Mr pore size. These results show that the inhibitory effect on DNA synthesis is mediated by TGF-β1-like and TGF-β2-like molecules.
In addition, acid-treated CM as well as purified TGF-β inhibited differentiation of pre-adipocytes. Untreated pre-adipocyte
CM, but not mature adipocyte CM, spontaneously inhibited adipocyte differentiation. Together, these findings indicate that
pre-adipocytes spontaneously activate their own secreted TGF-β, whereas mature adipocytes do not, and suggest that activation
of TGF-β has a potent negative regulatory effect on adipocyte differentiation and tumor growth. Thus, TGF-β may be an important
modulator of tumor growth and adipocyte differentiation via both paracrine and autocrine mechanisms. These findings emphasize
the importance of adipocyte-tumor interactions in the regulation of tumor microenvironment. 相似文献